The crucial role of cadmium acetate-induced conformational restriction in microscopic structure and stability of polystyrene-block-polyvinyl pyridine thin films

Block copolymers (BCPs) with inorganic components gained ground as a useful material with a broad range of applications. It is still a matter of discussion what influences of inorganic components on block copolymer structures. In this work we present the critical role of conformationally restricted effect by cadmium acetate (Cd(Ac)2) on microscopic structure and film stability of polystyrene-block-poly(2-vinylpyridine) (S2VP) and polystyrene-block-poly(4-vinylpyridine) (S4VP). The influence of ion concentration, coordination type, as well as physical ageing on micelles and films were investigated and discussed. It was revealed that the coordination type played a critical role in both micelle and thin film morphology. As ion concentration increased, the intermolecular coordination between Cd(Ac)2 and S4VP led to significant micelle coalescence and a decrease of film stability. However, intramolecular coordination between Cd(Ac)2 and S2VP only affected the micelle size. The film prepared from a physically aged low Cd2+ concentration S4VP solution formed mesoporous structure. AFM and GISAXS results showed excellent lateral ordering within mesoporous films. These results suggest a facile procedure for the preparation of block copolymer mesoporous structures which can provide the base for highly functional materials such as highly efficient catalysts, photonic devices, and photovoltaic films.